[LT] Why specifics about helmets and neck?

[Dustin]

Originally Posted by LazarusDarkeyes

I'm having trouble nailing down the specific trait(s) of the Greathelm that provoke the Tunnel Vision...

I think it's the combination of:
1) being a second rigid helmet layered on top of an underhelm (thus at a greater distance from the eyes), and
2) providing small enough eyeholes that the eyes use Chinks rules through the Greathelm.